Separation prevention device for pipe joint

ABSTRACT

A separation prevention device for a pipe joint has disengagement prevention members and a press member. The disengagement prevention members are disposed at a plurality of locations in a circumferential direction of the pipe, on an inner peripheral surface of an engaging tool or of a receiving opening itself and which are formed with claws. The press member presses the disengagement prevention member radially inward of the pipe and which engages the claw with the outer peripheral surface of an inserting opening. The claw of the disengagement prevention member and the claw of the disengagement prevention member which is adjacent to the former disengagement prevention member in the circumferential direction of the pipe are arranged so as to overlap on each other in the axial direction of the pipe in a state where the claws are engaged with the outer peripheral surface of the inserting opening.

TECHNICAL FIELD

The present invention relates to a separation prevention device for apipe joint which prevents a receiving opening and an inserting openinginserted into and connected to the receiving opening from separatingfrom each other in an axial direction thereof.

BACKGROUND ART

As such a separation prevention device for a pipe joint, there is knowna separation prevention device including disengagement preventionmembers disposed at a plurality of locations in a circumferentialdirection of the pipe on an inner peripheral surface of an engaging toolwhich engages with a receiving opening or an inner peripheral surface ofthe receiving opening itself, and a press member which presses thedisengagement prevention members inward in the radial direction of thepipe, as disclosed in Patent Documents 1 and 2. A claw is formed on theinner peripheral surface of the disengagement prevention member. Thedisengagement prevention member is pressed by the press member, the clawis made to bite into an outer peripheral surface of the insertingopening and engage with the outer peripheral surface, thereby exhibitinga separation preventing effect against a separating force of thereceiving opening and the inserting opening in the axial direction ofthe pipe.

One example of the conventional separation prevention device of a pipejoint will be described with reference to FIGS. 11 to 15. The samereference numerals are attached to the same members and positions as themembers and positions described in a first embodiment according to thepresent invention mentioned below, and an overlapping description willnot be repeated. As shown in FIGS. 11 to 13, a pressing ring 14 isengaged with a receiving opening 1 in a state where the pressing ring 14is fitted over an inserting opening 2, the pressing ring 14 presses aseal material 3 inserted into the receiving opening 1 and compresses theseal material 3 to a sealed state. FIG. 12 is a cross sectional view asseen from an arrow F-F in FIG. 11. FIG. 13 is a cross sectional view asseen from an arrow G-G in FIG. 11

FIG. 14 is a development view of the inner peripheral surface of thepressing ring 14 as viewed from the direction of an arrow H in FIG. 11.Recesses 19 are formed at a plurality of locations in an innerperipheral surface 14 a of the pressing ring 14 at equal distances fromone another in the circumferential direction of the pipe. The recesses19 open toward the inserting opening 2. A disengagement preventionmember 16 having a claw 18 is accommodated in each of the recesses 19. Ascrew hole is formed in each of the recesses 19 radially outward of thepipe, and a pressing bolt 17 as the press member is threadedly engagedwith the screw hole. The separation preventing effect of the pipe jointis exhibited by operating the pressing bolt 17 to press thedisengagement prevention member 16 radially inward of the pipe, and bymaking the claws 18 bite into and engage with the outer peripheralsurface of the inserting opening 2.

According to the separation prevention device, however, it was foundthat when the claws 18 of the disengagement prevention members 16 weremade to bite into and engage with the outer peripheral surface of theinserting opening 2 as shown in FIG. 15, in a material limit regionwhere a pipe is deformed, stress concentration occurred due to pipedeformation in a non-contact region Y formed between contact regions Xof the claw, and a crack was generated in a lining layer M of the innerperipheral surface of the pipe in some cases. The crack is frequentlygenerated especially at a central portion of the non-contact region Y.It is conceived that this is because a shearing stress generated nearends of the claws 18 which are adjacent to each other in thecircumferential direction of the pipe acts on the lining layer M at thecentral portion of the non-contact region Y.

In the separation prevention device in which the disengagementprevention members are disposed at the plurality of locations in thecircumferential direction of the pipe, since a ratio of a length of thecontact region of the claw in the circumferential direction of the pipewith respect to the outer peripheral surface of the inserting opening isabout 80 to 90% at most, in order to enhance the separation preventingeffect, there is room for improvement of the rate. Particularly, thereis a tendency that it is difficult to prevent the separation againststrong external forces caused by an earthquake or differentialsettlement, and it is strongly desired to propose a technique forimproving this.

Patent Document 1: Japanese Unexamined Patent Publication No. 61-88091

Patent Document 2: Japanese Unexamined Patent Publication No. 2005-3207

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

The present invention has been accomplished in view of the abovecircumstances, and it is an object of the present invention to provide aseparation prevention device for a pipe joint capable of preventing alining layer of an inner peripheral surface of a pipe from beingdamaged, and capable of enhancing separation preventing effect.

Means for Solving the Problems

The object can be achieved by the following present invention. That is,the present invention provides a separation prevention device for a pipejoint which prevents a receiving opening and an inserting opening whichis inserted into and connected to the receiving opening from beingseparated from each other in an axial direction of the pipe, comprisingdisengagement prevention members which are disposed at a plurality oflocations in a circumferential direction of the pipe, on an innerperipheral surface of an engaging tool which is engaged with thereceiving opening in a state where the receiving opening is fitted overthe inserting opening or on an inner peripheral surface of the receivingopening itself, and which is formed with claws capable of biting into anouter peripheral surface of the inserting opening and a press memberwhich presses the disengagement prevention member radially inward of thepipe and which engages the claw with the outer peripheral surface of theinserting opening, wherein the claw of the disengagement preventionmember and the claw of the disengagement prevention member which isadjacent to the former disengagement prevention member in thecircumferential direction of the pipe are arranged so as to overlap oneach other in the axial direction of the pipe in a state where the clawsare engaged with the outer peripheral surface of the inserting opening.

According to the separation prevention device for a pipe joint of thepresent invention, the claw of the disengagement prevention member andthe claw of the disengagement prevention member which is adjacent to theformer disengagement prevention member in the circumferential directionof the pipe are arranged so as to overlap on each other in the axialdirection of the pipe in a state where the claws are engaged with theouter peripheral surface of the inserting opening. Therefore, thecontact region of the claws can be continuous in the circumferentialdirection of the pipe between the adjacent disengagement preventionmembers. Therefore, stress concentration caused by deformation of thepipe when the claw bites into and engages with the outer peripheralsurface of the inserting opening can be suppressed, and it is possibleto avoid damage such as a crack in the lining layer. Further, accordingto the present invention, since the claws of the adjacent disengagementprevention members are disposed as described above, the ratio of thelength of the contact region of the claw in the circumferentialdirection of the pipe with respect to the outer peripheral surface ofthe inserting opening can be increased. Accordingly, a separationpreventing effect can be appropriately exhibited against a strongexternal force caused by an earthquake or differential settlement.

In the present invention, it is preferable that the disengagementprevention members disposed at the plurality of locations in thecircumferential direction of the pipe are accommodated in an annulargroove which opens toward the inserting opening in the inner peripheralsurface of the engaging tool or the receiving opening itself. With thisstructure, the disengagement prevention members can be collectivelyaccommodated in the annular groove, and the structure can be simplifiedas compared with the conventional case in which the disengagementprevention members are separately accommodated in recesses.

In the above structure, it is preferable that the two claws extending inthe circumferential direction of the pipe are formed on the innerperipheral surface of the disengagement prevention member, and one ofthe claws is disposed at a distance from the other claw in the axialdirection of the pipe and whose both ends are deviated in position inthe circumferential direction of the pipe. With this structure, engagingeffect of the claw with respect to the outer peripheral surface of theinserting opening can be exhibited stably, and the claws can beappropriately disposed such that they are overlapped on each other inthe axial direction of the pipe between the disengagement preventionmembers which are adjacent in the circumferential direction of the pipe.

In the above structure, it is preferable that a contact region of theclaw can be formed on the entire region of the inserting opening in thecircumferential direction of the pipe. With this structure, damage suchas a crack in the lining layer can be avoided over the entire region inthe inserting opening of the circumferential direction of the pipe, andthe separation preventing effect can be appropriately enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional front view showing a first embodiment of aseparation prevention device for a pipe joint of the present invention.

FIG. 2 is a cross sectional view as seen from an arrow A-A in FIG. 1.

FIG. 3 is a cross sectional view as seen from an arrow B-B in FIG. 1.

FIG. 4 is a development view of an inner peripheral surface of apressing ring as viewed from the direction of an arrow C in FIG. 1.

FIG. 5 is a diagram of disengagement prevention members and pressingbolts as viewed from a receiving opening along an axial direction of apipe.

FIG. 6 is a sectional front view showing a second embodiment of aseparation prevention device for a pipe joint of the present invention.

FIG. 7 is a cross sectional view as seen from an arrow D-D in FIG. 6.

FIG. 8 is a cross sectional view as seen from an arrow E-E in FIG. 6.

FIG. 9 is a plan view showing an inner peripheral surface ofdisengagement prevention members according to another embodiment of thepresent invention.

FIG. 10 is a plan view showing an inner peripheral surface ofdisengagement prevention members according to another embodiment of thepresent invention.

FIG. 11 is a sectional front view showing one example of a conventionalseparation prevention device for a pipe joint.

FIG. 12 is a cross sectional view as seen from an arrow F-F in FIG. 11.

FIG. 13 is a cross sectional view as seen from an arrow G-G in FIG. 11.

FIG. 14 is a development view of an inner peripheral surface of apressing ring as viewed from the direction of an arrow H in FIG. 11.

FIG. 15 is a diagram used for describing contact regions and non-contactregions of a claw.

DESCRIPTION OF THE REFERENCE SYMBOLS

-   1 Receiving opening-   2 Inserting opening-   3 Seal material-   4 Pressing ring (engaging tool)-   5 Fastening tool-   6 Disengagement prevention member-   7 Pressing bolt (press member)-   8 Claw-   9 Annular groove-   10 Overlapped portion-   P Fluid pipe-   X Contact region of claw

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be explained with reference tothe drawings.

First Embodiment

FIG. 1 is a sectional front view showing a first embodiment of aseparation prevention device for a pipe joint of the present invention.FIG. 2 is a cross sectional view as seen from an arrow A-A in FIG. 1.FIG. 3 is a cross sectional view as seen from an arrow B-B in FIG. 1. Ina pipe joint of fluid pipes P such as water pipes, gas pipes and plantpipes, the separation prevention device prevents a receiving opening 1of one of the fluid pipes P and an inserting opening 2 of the otherfluid pipe P inserted into and connected to the receiving opening 1 fromseparating from each other in an axial direction of the pipe (directionperpendicular to a sheet plane of FIG. 1).

An annular seal material 3 is disposed on a pipe joint of the fluidpipes P. The seal material 3 can seal between an inner peripheralsurface 1 a of the receiving opening 1 and an outer peripheral surface 2a of the inserting opening 2. The seal material 3 is pressed by acast-iron pressing ring 4 (corresponding to the engaging tool) from theaxial direction of the pipe, and is compressed such that an appropriatesealed state (water-tight state if the pipe is a water pipe) isobtained. A synthetic rubber such as styrene-butadiene rubber is shownas the seal material 3.

The pressing ring 4 can be fitted over the inserting opening 2. As shownin FIG. 3, the pressing ring 4 is fitted over the inserting opening 2and in this state, the pressing ring 4 is engaged with the receivingopening 1. The pressing ring 4 and the receiving opening 1 are engagedwith each other by a fastening tool 5 which detachably fixes andconnects the pressing ring 4 and the receiving opening 1 with each otherfrom the axial direction of the pipe. The fastening tool 5 includes aT-head bolt 51 and a nut 52. The T-head bolt 51 is inserted through abolt insertion hole 1 b formed in a flange 11 of the receiving opening 1and a bolt insertion hole 4 b formed in a projection piece 41 of thepressing ring 4. The nut 52 is threadedly engaged with a screw shaft ofthe T-head bolt 51. The seal material 3 is compressed by relativeapproaching movement between the pressing ring 4 and the receivingopening 1 caused by the fastening operation of the T-head bolt 51 andthe nut 52, and the above-described sealed state can be obtained.

Although the present embodiment shows an example where pressing ring 4is of annular shape and is integrally formed, the present invention isnot limited thereto, and it is possible to employ a split-type pressingring in which two or more divided pieces are annularly assembled. Anannular groove 9 opening toward the inserting opening 2 is formed in aninner peripheral surface 4 a of the pressing ring 4, and metaldisengagement prevention members 6 are accommodated in the annulargroove 9. As shown in FIG. 1, the disengagement prevention members 6 aredisposed at a plurality of locations (fourteen locations in the presentembodiment) in the circumferential direction of the pipe. Claws 8capable of biting into the outer peripheral surface 2 a of the insertingopening 2 are formed on the inner peripheral surface of thedisengagement prevention members 6.

A screw hole 4 c penetrating an outer peripheral wall of the annulargroove 9 is formed in a central portion of each of the disengagementprevention members 6 in its circumferential direction radially outward.A pressing bolt 7 (corresponding to the press member) is threadedlyengaged with each of the screw holes 4 c from outside in the radialdirection of the pipe. In this manner, by operating the pressing bolt 7,the disengagement prevention member 6 can be pressed radially inward ofthe pipe, and the claws 8 can bite into and engage with the outerperipheral surface 2 a of the inserting opening 2.

An inclined surface 61 whose diameter becomes greater toward thereceiving opening 1 is formed on a central portion of an outer surfaceof the disengagement prevention member 6 in the circumferentialdirection. The pressing bolt 7 inclines with respect to a directionperpendicular to the axial direction of the inserting opening 2 so as topress the disengagement prevention member 6 through the inclined surface61. Therefore, when an external force separating the receiving opening 1and the inserting opening 2 from each other in the axial direction ofthe pipe is applied, the disengagement prevention member 6 is pressedradially inward of the pipe by wedge effect, and engaging effect causedby the claws 8 can be enhanced.

FIG. 4 is a development view of the inner peripheral surface 4 a of thepressing ring 4 as viewed from the direction of an arrow C in FIG. 1. Anupper side in FIG. 4 is on the side of the receiving opening 1. FIG. 5is a diagram of the disengagement prevention members 6 and the pressingbolts 7 as viewed from the receiving opening 1 side along the axialdirection of the pipe. In the present embodiment, two kinds ofdisengagement prevention members, i.e., disengagement prevention members6A and disengagement prevention members 6B are employed as thedisengagement prevention members 6, and they are disposed alternatelyadjacent to each other in the circumferential direction of the pipe.

Two claws 8A1 and 8A2 continuously extending in the circumferentialdirection of the pipe are integrally formed on the inner peripheralsurface of the disengagement prevention member 6A as the claws 8. Theclaws 8A1 and 8A2 project so as to form triangular cross sections asshown in FIG. 2, and are disposed in parallel to each other at apredetermined distance from each other in the axial direction of thepipe. Similarly, two claws 8B1 and 8B2 are also formed on the innerperipheral surface of the disengagement prevention member 6B, the claw8B1 is disposed at the same position as the claw 8A1 in the axialdirection of the pipe, and the claw 8B2 is disposed at the same positionas the claw 8A2 in the axial direction of the pipe. A tip end of theclaw 8 is curved in an arc form as viewed in the axial direction of thepipe, and a curvature thereof is set such that it is substantially thesame as that of the outer peripheral surface 2 a of the insertingopening 2.

Both ends of one of the two claws of the disengagement preventionmembers 6A and 6B are deviated in the circumferential direction of thepipe from both ends of the other claw. More specifically, the claw 8A1of the disengagement prevention member 6A is longer than the claw 8A2,and the claw 8A1 protrudes from both ends of the claw 8A2 in thecircumferential direction of the pipe. The claw 8B2 of the disengagementprevention member 6B is longer than the claw 8B1, and the claw 8B2protrudes from both ends of the claw 8B1 in the circumferentialdirection of the pipe. The claw 8A1 of the disengagement preventionmember 6A and the claw 8B2 of the disengagement prevention member 6B areoverlapped on each other in the axial direction of the pipe, and anoverlapped portion 10 is formed.

In this manner, as shown in FIG. 5, a contact region X of the claw 8 cancontinuously be formed in the circumferential direction of the pipebetween the adjacent disengagement prevention members 6A and 6B, stressconcentration caused by deformation of the pipe at the inserting opening2 can be suppressed, and damage such as a crack in a lining layer M ofthe inner peripheral surface of the pipe can be prevented. Further, theratio of the length of the contact region X of the claw 8 in thecircumferential direction of the pipe with respect to the outerperipheral surface 2 a of the inserting opening 2 is increased.Accordingly, a separation preventing effect can be appropriatelyexhibited against a strong external force caused by an earthquake ordifferential settlement.

In the present invention, to exhibit the damage preventing effect of thelining layer M over the entire region of the inserting opening 2 in thecircumferential direction of the pipe, and to further enhance theseparation preventing effect of the pipe joint, it is preferable thatthe overlapped portion 10 is formed between all of the disengagementprevention members 6A and the disengagement prevention members 6B, andthe contact region X of the claw 8 is formed over the entire region ofthe inserting opening 2 in the circumferential direction of the pipe. Insuch a case, a ratio of the length of the contact region X of the claw 8in the circumferential direction of the pipe with respect to the outerperipheral surface 2 a of the inserting opening 2 is 100%.

A state where the above-described overlapped portion 10 is formed may beobtained when the claws 8 of the disengagement prevention members 6A and6B are engaged with the outer peripheral surface 2 a of the insertingopening 2. Since a moving stroke of the disengagement prevention member6 in the radial direction of the pipe is usually a few millimeters dueto the structure of the pressing ring 4, the overlapped portion 10 mayalready be formed before the disengagement prevention members 6A and 6Bare pressed as in the present embodiment.

To appropriately form the overlapped portion 10 and reliably exhibit theabove-described effect, in the present invention, it is preferable toincrease the length L of the overlapped portion 10 in thecircumferential direction of the pipe as long as possible within a rangewhere the strength with respect to a load can be obtained, and thelength L of the overlapped portion 10 in the present embodiment isexemplified in a range of 5 to 8 mm. A gap G between the claws 8 whichare adjacent in the circumferential direction of the pipe is notparticularly limited, but in the present embodiment, an example of thegap is in a range of 1 to 3 mm in a state where the claws 8 are engagedwith the outer peripheral surface 2 a of the inserting opening 2.

In the present embodiment, as shown in FIG. 4, portions where the claws8A1 and 8A2 are formed at both ends of the inner peripheral surface ofthe disengagement prevention member 6A in the circumferential directionof the pipe are provided substantially in parallel to the axialdirection of the pipe, and portions located between these formerportions are inclined with respect to the axial direction of the pipe.In this manner, the thicknesses of the both ends of the claws 8A1 and8A2 are secured, and the engaging effect to the outer peripheral surface2 a of the inserting opening 2 can effectively be exhibited. Thedisengagement prevention member 6B has the same structure and canexhibit the same effect.

In the present embodiment, the plurality of disengagement preventionmembers is collectively accommodated in one annular groove 9. Therefore,the structure of the pressing ring can be simplified as compared withthe conventional case where the disengagement prevention members areseparately accommodated in the recesses.

Second Embodiment

In the first embodiment, the separation prevention device for a pipejoint of the present invention is applied to a so-called mechanical pipejoint in which the pressing ring and the receiving opening are formedrelatively close to each other, thereby compressing the seal material toestablish a sealed state. However, the present invention is not limitedthereto, and the separation prevention device may be applied to aso-called slip-on pipe joint in which the receiving opening has aself-sealing function. An example in which the separation preventiondevice of the present invention is applied to the slip-on pipe jointwill be described.

FIG. 6 is a sectional front view showing a second embodiment of aseparation prevention device for a pipe joint of the present invention.FIG. 7 is a cross sectional view as seen from an arrow D-D in FIG. 6.FIG. 8 is a cross sectional view as seen from an arrow E-E in FIG. 6.Since a second embodiment has similar structure and operation to thefirst embodiment excluding a structure explained below, portions of thesecond embodiment which are common to those of the first embodiment willnot be repeated here, and different portions will mainly be explained.

In the second embodiment, disengagement prevention members 6 aredisposed at a plurality of locations on an inner peripheral surface of areceiving opening 31 itself in the circumferential direction of thepipe. The inner peripheral surface 31 a of the receiving opening 31 isprovided with an annular recess 32 for accommodating a seal material 39therein, and an annular groove 33 which is located closer to a tip endthan the annular recess 32 and which opens toward the inserting opening2. A disengagement prevention member 38 is accommodated in the annulargroove 33. Screw holes 34 penetrating an outer peripheral wall of theannular groove 33 are formed in a central portion of the disengagementprevention member 38 in the circumferential direction thereof atlocations radially outward of the pipe. Pressing bolts 35 are insertedinto the screw holes 34, respectively in a direction perpendicular tothe axis of the inserting opening 2. The same structure as that of thedisengagement prevention member 6 described in the first embodiment canbe employed for the disengagement prevention member 38.

According to this structure, by operating the pressing bolt 35 to pressthe disengagement prevention member 38 radially inward of the pipe, theclaws of the disengagement prevention members 38 can bite into the outerperipheral surface of the inserting opening 2. At that time, the contactregions of the claws are continuously formed in the circumferentialdirection of the pipe between the adjacent disengagement preventionmembers 38, similar to the first embodiment. Therefore, it is possibleto prevent the lining layer M from being damaged, and to exhibitexcellent separation preventing effect of the pipe joint.

Other Embodiments

(1) The present invention is not limited to the above-describedembodiments, and various changes may be made without departing from thesubject matter of the present invention. A projecting amount, a crosssection shape, a curvature of the claw, a length of the disengagementprevention member in the circumferential direction of the pipe canappropriately be changed. Although the disengagement prevention membersare disposed at fourteen locations in the circumferential direction ofthe pipe in the above-described embodiment, the present invention is notlimited thereto, and the disengagement prevention members may bedisposed at four to twenty eight locations in the circumferentialdirection of the pipe.

(2) The pressing bolt as the press member is inclined with respect to orin parallel to the direction perpendicular to the axial direction of theinserting opening in the above-described embodiment, the presentinvention is not limited thereto, and the pressing bolt may be providedin parallel to the axial direction of the pipe. For example, it ispossible to employ such a structure that a side surface of the tip endof the pressing bolt is tapered, the tapered surface is disposed suchthat it can come into contact with the outer peripheral surface of thedisengagement prevention member, and the pressing bolt is made to moveforward, thereby pressing the disengagement prevention member radiallyinward of the pipe.

(3) Although the both ends of one of the two claws of the disengagementprevention member project more than the other claw in thecircumferential direction of the pipe in the above-described embodiment,the present invention is not limited thereto. In the case of adisengagement prevention member 6C shown in FIG. 9, a right end of theclaw 8C1 shown in FIG. 9 projects more than the claw 8C2 in thecircumferential direction of the pipe, a left end of the claw 8C2 inFIG. 9 projects more than the claw 8C1 in the circumferential directionof the pipe, the claw 8C1 of the disengagement prevention member 6C andthe claw 8C2 thereof which is adjacent to the claw 8C1 are overlapped oneach other in the axial direction of the pipe, thereby forming anoverlapped portion 20. In this case, since one kind of disengagementprevention member 6C suffices, the number of parts can be reduced.

(4) Although the two claws are formed on the disengagement preventionmember in the above-described embodiment, the number of claws is notlimited thereto, and the number thereof may be one, three or more. FIG.10 shows an example in which one claw is formed on the disengagementprevention members 6D and 6E. A claw 8D1 of the disengagement preventionmember 6D is overlapped on a claw 8E2 of the disengagement preventionmember 6E in the axial direction of the pipe, and thereby an overlappedportion 30 is formed.

1. A separation prevention device for a pipe joint which prevents areceiving opening and an inserting opening which is inserted into andconnected to the receiving opening from being separated from each otherin an axial direction of a pipe to be joined by the pipe joint,comprising: disengagement prevention members which are disposed at aplurality of locations in a circumferential direction of the pipe, on aninner peripheral surface of an engaging tool which is engaged with thereceiving opening in a state where the receiving opening is fitted overthe inserting opening or on an inner peripheral surface of the receivingopening itself, and which is formed with claws capable of biting into anouter peripheral surface of the inserting opening; and a press memberwhich presses the disengagement prevention member radially inward of thepipe and which engages the claw with the outer peripheral surface of theinserting opening, wherein the claw of the disengagement preventionmember and a claw of an adjacent disengagement prevention member whichis adjacent in the circumferential direction of the pipe are arranged soas to overlap on each other in the axial direction of the pipe in astate where the claws are engaged with the outer peripheral surface ofthe inserting opening.
 2. The separation prevention device for the pipejoint according to claim 1, wherein the disengagement prevention membersdisposed at the plurality of locations in the circumferential directionof the pipe are accommodated in an annular groove which opens toward theinserting opening in the inner peripheral surface of the engaging toolor the receiving opening itself.
 3. The separation prevention device forthe pipe joint according to claim 1, wherein two claws extending in thecircumferential direction of the pipe are formed on the inner peripheralsurface of the disengagement prevention member, and one of the claws isdisposed at a distance from the other claw in the axial direction of thepipe and whose both ends are deviated in position in the circumferentialdirection of the pipe.
 4. The separation prevention device for the pipejoint according to claim 1, wherein a contact region of the claw can beformed on the entire region of the inserting opening in thecircumferential direction of the pipe.
 5. A separation prevention devicefor a pipe joint, which connects a first pipe having a receiving openingand a second pipe having a inserting opening, comprising: disengagementpreventer disposed at a plurality of locations in a circumferentialdirection of the first pipe on an inner peripheral surface thereof atthe receiving opening, wherein said disengagement preventer comprises aclaw to press onto an outer peripheral surface of the second pipe at theinserting opening; and a press applying pressure to the disengagementpreventer in a direction radially inward of the first pipe; wherein theclaws of the disengagement preventer adjacent to each other in thecircumferential direction of the first pipe overlap in an axialdirection of the first pipe and the second pipe being connected.
 6. Theseparation prevention device according to claim 1 further comprising anengaging tool which engages with the first pipe at the receiving openingwherein the disengagement preventers are disposed at a plurality oflocations in a circumferential direction of the first pipe on an innerperipheral surface of the engaging tool.
 7. The separation preventiondevice according to claim 5 wherein the first pipe comprise an annulargroove on the inner peripheral surface at the receiving opening whichopens toward radially inward of the first pipe, and the disengagementpreventers are disposed at the plurality of locations therein.
 8. Theseparation prevention device according to claim 6 wherein the engagingtool comprise an annular groove on the inner peripheral surface whichopens toward radially inward of the first pipe, and the disengagementpreventer are disposed at the plurality of locations therein.
 9. Theseparation prevention device according to claim 5, wherein thedisengagement preventer comprises two claws extending in thecircumferential direction of the first pipe and the claws are disposedin parallel from each other and offset in the circumferential directionof the first pipe.
 10. The separation prevention device according toclaim 6, wherein the disengagement preventer comprises two clawsextending in the circumferential direction of the first pipe and theclaws are disposed in parallel from each other and offset in thecircumferential direction of the first pipe.
 11. The separationprevention device according to claim 5, wherein a plurality of contactregions of the claws extends entirely over a circumference of the secondpipe at the inserting opening while the first pipe and the second pipebeing connected.
 12. The separation prevention device according to claim6, wherein a plurality of contact regions of the claws extends entirelyover circumference of the second pipe at the inserting opening while thefirst pipe and the second pipe being connected.